JPH11125993A - Both-surface image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a proper both-surface image even on different conditions by executing the mirror-image rotation of an original image on a stage that the toner image of a back surface is formed when the effective image area of the original image and that of a transfer material are in identical directional relation. SOLUTION: When the effective image area of the original image is in the identical directional relation with respect to that of the transfer material at the back-surface image forming time, at the time of forming the toner image on the transfer material, the mirror-image rotation of the original image is executed on the stage that the toner image of the back surface is formed in a data selector (I) B17. The image data of the front surface accessed from a memory B14 is processed by an image processing part (II) B16 and rotated by 90 deg. by the selector (I) B17. Thereafter, it is inputted to a memory for outputting front-surface image data B18A. Next, the mirror-image rotation processing or the (mirror-image + 90 deg.) rotation processing of the image data of the back surface is executed according to the condition. Thereafter, it is inputted to a memory for outputting back-surface image data B18B. Then, the image data of the back surface is outputted to an exposure unit 12 and the back-surface image is formed on a photoreceptor drum 10. Next, the front-surface image is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to copying in which a charging means, an image exposing means and a developing means are arranged around an image carrier to transfer and fix a toner image formed on the image carrier to both sides of a transfer material. The present invention relates to an electrophotographic double-sided image forming apparatus such as a printer.

[0002]

2. Description of the Related Art Conventionally, in double-sided copying, an image on one side formed on an image carrier is transferred and fixed on a transfer material, and this is temporarily stored in a two-sided reversing paper feeder, and the image bearing is again performed. A method has been adopted in which a transfer material is fed from a double-sided reversing sheet feeder in synchronization with an image formed on the body, and an image on the other surface is transferred and fixed onto the transfer material.

In this double-sided copying apparatus, as described above, the transfer of the transfer material, such as feeding to the two-sided reversing paper feeder and passing through the fixing device twice, is performed, so that the reliability of transfer of the transfer material is low. And wrinkles of the transfer material.
Further, as is well known, there is another problem that the copying material takes a lot of processing time because the transfer distance of the transfer material is long.

On the other hand, JP-B-49-37538, JP-B-54-28740, and JP-A-1-444.
No. 57, Japanese Patent Application Laid-Open No. 4-214576, and the like have proposed a device in which a toner image is formed on both surfaces of a transfer material and then fixed once.

Further, the present applicant provides an apparatus for transferring a toner image to both sides of a transfer material and simultaneously fixing the transfer material having the toner images on both sides by providing two image carrying means and two transfer means. The authors conducted a study on a double-sided image forming apparatus that had high reliability in transfer material transfer, did not cause jams and wrinkles, and could significantly increase the processing speed of double-sided copying.

In the above-described double-sided image forming apparatus, the transfer material on which the toner images have been transferred on the front and back surfaces only needs to be passed through the fixing device once, so that the transfer material transfer reliability is high, and the transfer material transfer path is increased. The processing speed of copying can be shortened and shortened.

[0007]

However, there is also a problem on the one hand using such excellent characteristics. As will be described in detail later, in the image forming apparatus of the present invention, the back side image formed on the image forming body is transferred onto the intermediate transfer body, and the front side image formed on the image forming body and the intermediate transfer body again. The upper back side image is transferred to the front and back sides of the recording paper, and this is fixed collectively. In this case, the front side image on the recording paper is an image obtained by one transfer. On the other hand, the back side image is an image obtained by two transfers. The fact that the number of times of transfer is different between the front image and the back image is bad if the toner image formed on the image forming body is the same for the front image and the back image.

Further, this means that the shape of the original (the effective image area of the original image) as viewed from the optical reading direction of the original and the shape of the transfer paper (the effective image area of the transfer material) as viewed from the discharge direction are the same. The case and the case of different directions are more complicated. For example, there is a case where a vertically long transfer sheet is obtained from a vertically long document, and a case where a vertically long transfer sheet is obtained from a horizontally long document. Further, the case where a double-sided image is to be obtained on a transfer sheet from a portrait document on the front side and a landscape document on the back side is further complicated.

It is an object of the present invention to provide a double-sided image forming apparatus capable of obtaining an appropriate double-sided image of such an original image and a transfer material under various different conditions.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a first image carrying means for forming an original image as a toner image on a surface thereof by a toner image forming means and carrying the toner image; A toner image carried on the means is collectively transferred, a second image carrying means for carrying the transferred toner image on the surface, and a toner image carried on the first image carrying means. A first transfer unit that transfers the image to one surface (front surface) of the material; and a second unit that transfers the toner image carried by the second image holding device to the other surface (back surface) of the transfer material.
And a fixing device for fixing a toner image transferred to both surfaces of the transfer material, wherein a toner image is formed on the transfer material. A double-sided image forming apparatus, wherein when the effective image area of the original image is in the same direction as the effective image area, the original image is mirror-rotated at the stage of forming the toner image on the back surface; The first image carrying means for forming the original image on the surface as a toner image by the toner image forming means and carrying the toner image, and the toner image carried on the first image carrying means are collectively formed. A second image carrying means for carrying the transferred and transferred toner image on the surface, and a second image carrying means for transferring the toner image carried on the first image carrying means to one surface (surface) of the transfer material. 1 transfer means and the second image transfer means. Double-sided image having a second transfer unit for transferring the toner image carried by the unit to the other surface (back surface) of the transfer material, and a fixing device for fixing the toner image transferred to both surfaces of the transfer material A forming device for forming a toner image on a surface when an effective image area of an original image is perpendicular to an effective image area of a transfer material when forming a toner image on the transfer material; A two-sided image forming apparatus wherein the original image is rotated by 90 degrees in a step (the invention of claim 2); and a second image forming apparatus which forms the original image as a toner image on the surface by toner image forming means and carries the toner image A first image carrying unit, a second image carrying unit onto which a toner image carried on the first image carrying unit is collectively transferred, and carrying the transferred toner image on a surface; Carried by the image carrying means of A first transfer unit for transferring the toner image to one surface (front surface) of the transfer material; and a toner image carried by the second image carrying unit to the other surface (back surface) of the transfer material. What is claimed is: 1. A double-sided image forming apparatus, comprising: a second transfer unit; and a fixing device for fixing a toner image transferred to both sides of the transfer material. When the effective image area of the original image with respect to the effective image area of the material is in a vertical direction, the original image is reduced by 9 at the stage of forming the toner image on the back surface.
A two-sided image forming apparatus (the invention according to claim 3) characterized in that the original image is formed as a toner image on the surface by a toner image forming means, and the toner image is carried thereon. A first image carrying unit, a second image carrying unit onto which a toner image carried on the first image carrying unit is collectively transferred, and carrying the transferred toner image on a surface; A first transfer means for transferring the toner image carried by the image carrying means to one surface (front surface) of the transfer material; and a toner image carried by the second image carrying means to the transfer material. Second to transfer to the other side (back side)
And a fixing device for fixing the toner images transferred on both sides of the transfer material, wherein the effective image area of the transfer material and the effective image area of the original image have the same directional relationship. In some cases, the original image is mirror-image-rotated at the stage of forming the toner image on the back surface, and the toner image is formed on the front surface by the toner image forming means. Formed as
First image holding means for holding the toner image;
A toner image carried on the image carrying means is collectively transferred, a second image carrying means carrying the transferred toner image on the surface, and a toner carried on the first image carrying means. A first transfer unit that transfers an image to one surface (front surface) of the transfer material; and a first transfer unit that transfers the toner image carried by the second image holding device to the other surface (back surface) of the transfer material. 2. A double-sided image forming apparatus, comprising: a transfer unit of No. 2;
When the effective image area of the transfer material is perpendicular to the effective image area of the original image, the original image is rotated by 90 degrees and the mirror image is rotated at the stage of forming the toner image on the back surface to form a toner image on the front surface. A double-sided image forming apparatus, wherein an original image is rotated by 90 degrees in a step.
Invention).

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described below. FIG. 1 is a cross-sectional configuration diagram of hardware in a digital color image forming apparatus that enables double-sided image formation. The present invention is not limited to an image forming apparatus capable of forming a color image on both sides of a transfer material, but may be a monochrome digital copying machine capable of forming a double-sided image.

In FIG. 1, the color image forming apparatus includes an image reading section A, an image processing section B (not shown), and an image forming section C. The image reading section A serves as reading means and the image processing section B serves as a reading means. Corresponds to an image processing unit, and the image forming unit C corresponds to an image forming unit.

The image reading section A is capable of reading images recorded on both sides of the original. In the image reading section A, the originals 60 are stacked in page order from the lower side with the front side facing down. By the operation of the separating roller 52, the lowermost document is carried out toward the transport path 53. The conveyed original 60 is removed from the guide plate 61 urged to the position shown by the solid line, retracted to the position shown by the broken line, and fed onto the transparent platen glass 55 via the transport belt 54. Then, the document is temporarily stopped at the document reading position with the back face down.

An image of the back surface of the original 60 on the platen glass 55 is obtained from a first mirror unit 56 comprising an illumination lamp and a first mirror constituting a scanning optical system, and a second mirror and a third mirror located in a V-shape. The second mirror unit 57
Of the first mirror unit 56 at the speed V and the speed V / 2 in the same direction by the second mirror unit.
The image is read by the moving exposure, and is imaged on the light receiving surfaces of the image sensors CCD, which are three line sensors, through the projection lens 62 and the dichroic prism 63. The linear optical image formed on the image sensor CCD after color separation is photoelectrically converted into an electric signal (luminance signal) in sequence.

When the reading of the back side image is completed in the image reading section A, the original 60 is turned upside down through the reversing paper feed path 58 by the temporary reverse rotation of the conveyor belt 54, and again passed through the conveyor path 53. Through the platen glass 5
5, and is temporarily stopped at the document reading position with the front surface facing downward.

The surface image of the original 60 on the platen glass 55 is read by the above-mentioned scanning optical system, color-separated, and photoelectrically converted into an electric signal by the image sensor CCD.

The original 60 whose image has been read on the platen glass 55 is stacked on the tray 64 via the discharge roller 59 by the operation of the transport belt 54 so that the surface of the original 60 faces downward from the lower side. The paper is ejected.

An image signal (image data) of the original image read by the image reading section A is transmitted to an image processing section B described later.
After performing various image processing such as density conversion, filter processing, scaling processing, γ correction, front / back image correction processing, and image data rotation processing according to the present invention, the image data is output to the image forming unit C. .

The image forming section C forms an image on a recording sheet according to an input image signal by a laser printer using electrophotography.

In the image forming section C, the photosensitive drum 10, which is the first image carrier, is provided with a cylindrical base formed of a transparent member of, for example, optical glass or transparent acrylic resin. A photosensitive layer such as a layer, an a-Si layer, or an organic photosensitive layer (OPC) is formed on the outer periphery of the substrate, and is rotated clockwise as shown by an arrow in FIG. 1 in a grounded state.

As shown in the side sectional view of FIG. 2, the photosensitive drum 10 is a flange member 10a at both ends for engaging and fixing it.
And shaft 10b are fixedly mounted on the apparatus main body.
The gears G are integrally supported by the bearings 110a and 110b fitted in the flange members 10a and 10b at both ends, and are rotatably supported. As a result, it is rotated at a constant speed in a predetermined direction.

Scorotron charger 11 as charging means
Is used in an image forming process of each color of yellow (Y), magenta (M), cyan (C), and black (K), and is exposed in a direction orthogonal to a moving direction of the photosensitive drum 10 as an image forming body. It is installed facing the body drum 10,
It has a control grid maintained at a predetermined potential with respect to the above-mentioned organic photosensitive layer of the photosensitive drum 10 and a discharge electrode 11a composed of, for example, a sawtooth electrode, and performs a charging action by corona discharge having the same polarity as the toner (this embodiment). In the embodiment, the photosensitive drum 10 is given a uniform potential. Other wire electrodes can be used as the discharge electrode 11a.

The exposure unit 12 as an image exposure means for each color is arranged such that the exposure position on the photosensitive drum 10 is located between the discharge electrode 11a of the scorotron charger 11 and the developing position of the developing unit 13. Be placed.

The exposure unit 12 is a linear exposure element in which a plurality of LEDs (light emitting diodes) as image exposure light emitting elements arranged in the main scanning direction in parallel with the axis 110 of the photosensitive drum 10 are arranged in an array. The exposure unit 12a and the SELFOC lens 12b as an equal-magnification imaging element are mounted on a holder (not shown). An exposure unit 12 for each color, a uniform exposure device 12
c and a transfer simultaneous exposure unit 12 d are mounted and housed inside the base body of the photosensitive drum 10. The image data read by the image reading unit A and subjected to image processing by the image processing unit B is input as an electric signal to the exposure unit 12 for each color.

As the exposure element, an element in which a plurality of light-emitting elements such as FL (fluorescent light emission), EL (electroluminescence), and PL (plasma discharge) are arranged in an array is used. The light emission wavelength of the light emitting element used in this embodiment is usually in the range of 780 to 900 nm, which is high in transmittance of the Y, M, and C toners when performing image exposure from the outside. Since the exposure method is used, a shorter wavelength of 400 to 780 nm, which does not sufficiently transmit light to the color toner, may be used.

The developing unit 13 provided in accordance with the color sequence in which the image is formed and the rotating photosensitive drum is arranged in the color sequence.
In the present embodiment, the developing units 13 of Y and M are on the left side of the photosensitive drum 10 and the developing units 13 of C and K are on the right side of the photosensitive drum 10 with respect to the photosensitive drum 10 of FIG. And the developing casing 1 of the Y and M developing units 13
The scorotron chargers 11 for Y and M are disposed below 38, and the scorotron chargers 11 for C and K are disposed above the developing casing 138 of the C and K developing devices 13.

The developing device 13 as a developing means for each color includes
One-component or two-component developers of yellow (Y), magenta (M), cyan (C), and black (K) are accommodated, respectively, while maintaining a predetermined gap with respect to the peripheral surface of the photosensitive drum 10. At the developing position, for example, a thickness of 0.5 to 1 mm that rotates in the same direction as the rotation direction of the photosensitive drum 10,
The developing sleeve 131 is formed of a cylindrical non-magnetic stainless steel or aluminum material having an outer diameter of 15 to 25 mm.

The developing device 13 is moved to a predetermined distance from the photosensitive drum 10 by an abutting roller (not shown).
Developing device 1 for each color which is kept in
In the developing operation of the developing device 3, a developing bias to which a DC voltage or an AC voltage is further applied is applied to the developing sleeve 131, and a jumping development is performed by a one-component or two-component developer accommodated in the developing device, so that a negative charge is applied. A non-contact reversal development is performed in which a DC bias having the same polarity as the toner (in this embodiment, a negative polarity) is applied to the photosensitive drum 10 so that the toner adheres to the exposed portion.
The development interval accuracy at this time is 20 μm to prevent image unevenness.
Less than or equal to degree is required.

The developing unit 13 for each color described above converts the electrostatic latent image on the photosensitive drum 10 formed by the charging by the scorotron charger 11 and the image exposure by the exposure unit 12 into a non- In a non-contact state, the toner having the same polarity as the charged polarity (in the present embodiment, the photosensitive drum is negatively charged and the toner having a negative polarity) is reversely developed by a contact developing method.

When image recording is started, a gear G provided on a rear flange 10b of the photosensitive drum 10 is rotated through a driving gear by driving of a photosensitive member driving motor (not shown), and the photosensitive drum 10 is moved by an arrow in FIG. And at the same time, yellow (Y) on the left side of the photosensitive drum 10
The application of a potential to the photosensitive drum 10 is started by the charging action of the Y scorotron charger 11 disposed below the developing casing 138 of the developing device 13 of FIG.

After the photosensitive drum 10 is applied with an electric potential, the exposure by the first color signal, that is, the electric signal corresponding to the Y image data is started in the Y exposure unit 12, and the rotation of the photosensitive drum 10 causes the photosensitive drum 10 to rotate. An electrostatic latent image corresponding to the Y image of the original image is formed on the photosensitive layer on the surface.

The latent image is reversal-developed by the Y developing device 13 in a state where the developer on the developing sleeve is not in contact with the developer, and a yellow (Y) toner image is formed in accordance with the rotation of the photosensitive drum 10.

Next, the photosensitive drum 10 has a magenta (M) developing device 1 on the yellow (Y) toner image and further on the left of the photosensitive drum 10 and above the yellow (Y).
An electric signal corresponding to the second color signal of the M exposure unit 12, that is, the M image data, is applied by the charging action of the magenta (M) scorotron charger 11 disposed below the third developing casing 138. Is performed, and magenta (M) is formed on the yellow (Y) toner image by non-contact reversal development by the M developing unit 13.
Are formed in a superimposed manner.

By the same process, the developing casing 13 of the developing unit 13 for cyan (C) is located on the right side of the photosensitive drum 10.
The cyan (C) toner image corresponding to the third color signal is further obtained by the cyan (C) scorotron charger 11, the exposure unit 12 of C, and the developing unit 13 of C, which are arranged above the photoconductor 8 The black (K) scorotron charger 11, the exposure unit 12, and the developing device 13 are arranged on the right side of the drum 10 and below the developing casing 138 of the black (K) developing device 13 at the lower part of the fourth color by the fourth unit. A black (K) toner image corresponding to the signal is sequentially superposed, and a color toner image is formed on the peripheral surface within one rotation of the photosensitive drum 10 (toner image forming means).

Exposure unit 1 for Y, M, C and K
Exposure of the organic photosensitive layer of the photosensitive drum 10 by 2 is performed from the inside of the drum through the transparent substrate described above. Therefore, the exposure of the image corresponding to the second, third, and fourth color signals is performed without any influence from the previously formed toner image, and the same exposure as the image corresponding to the first color signal is performed. It is possible to form an electrostatic latent image.

By the above-described image forming process, a superimposed color toner image serving as a back side image is formed on a photosensitive drum 10 (image forming body) as an image forming body. The transfer unit 14 to which a DC voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied to the toner image in the transfer area 14b.
c (first transfer means), which is stretched between the driving roller 14d and the driven roller 14e, and is a toner image receiving body 14a (second image carrying means) provided near or in contact with the photosensitive drum 10. On the intermediate transfer member). At this time, for example, L
Simultaneous transfer exposure device 12d using ED (light emitting diode)
Is performed.

The toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is subjected to static elimination by the image forming body AC static eliminator 16 and then enters the cleaning device 19 or the photosensitive drum 10.
Cleaning blade 19a made of rubber material in contact with
In order to eliminate the history of the photoreceptor up to the previous print, the peripheral surface of the photoreceptor is removed by exposure by a uniform exposure unit 12c before charging using, for example, an LED (light emitting diode). Then, the next surface image is formed in a color image.

After the superimposed color toner image serving as the back surface image is formed on the toner image receiving member 14a as described above, the superposed toner image serving as the front surface image is successively formed on the photosensitive drum 10. It is formed in the same manner as the image forming process. At this time, the toner image receiver 14
The back image formed on the photosensitive drum 10 and the back image formed on the photosensitive drum 10 are synchronized in the transfer area 14b, and a toner image is formed as shown in FIG. The surface image formed at this time is the photosensitive drum 10
In the above, image data is changed by the image processing unit B described later so that the back side image formation is a mirror image of each other.

A paper feed cassette 15A in which recording paper P as a transfer material is stocked for each size as a transfer material storage means,
From 15B and 15C, the corresponding recording paper is sent out by the feeding roller 15a according to the instruction of the recording paper size,
The timing roller 1 is fed by the feeding roller 15b.
5c.

The recording paper P is driven by the timing roller 15c to form a color toner image of a front surface image carried on the photosensitive drum 10 and a color toner image of a rear surface image carried on the toner image receiver 14a. Are fed to the transfer area 14b in synchronization with the above. At this time, the recording paper P is charged to the same polarity as the toner by a paper charger 14f as a transfer material charging means, is attracted to the toner image receiver 14a, and is fed to the transfer area 14b. By charging the paper with the same polarity as the toner, the recording paper P is prevented from attracting to the toner image on the toner image receiver 14a or the toner image on the photoconductor drum 10 outside the transfer portion, and the toner image is disturbed. Has been prevented. Further, as the transfer material charging means, the toner image receiving member 1 is used.
It is also possible to use a conductive roller, a brush charger or the like capable of abutting and releasing the abutment on 4a.

A surface image on the peripheral surface of the photosensitive drum 10 is collectively recorded on a recording paper by a transfer unit 14c as a first transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in this embodiment) is applied. It is transferred to the upper surface side (front side) of P. At this time, the back surface image on the peripheral surface of the toner image receiver 14a is not transferred to the recording paper P but exists on the toner image receiver 14a. Next, a backside image on the peripheral surface of the toner image receiving body 14a is collectively recorded by a backside transfer unit 14g as a second transfer unit to which a voltage having a polarity opposite to that of the toner (positive polarity in the present embodiment) is applied. The image is transferred to the lower surface (back surface) of the paper P. At the time of transfer by the transfer device 14c, a transfer simultaneous exposure device 12d using, for example, an LED (light emitting diode) provided inside the photosensitive drum 10 to face the transfer device 14c so that good transfer is performed. Uniform exposure is performed.

Since the toner images of the respective colors overlap with each other, it is preferable that the toner in the upper layer and the toner in the lower layer of the toner layer are charged to the same polarity with the same charge amount in order to enable batch transfer. Accordingly, in the double-sided image formation in which the polarity of the color toner image formed on the toner image receiving body 14a is inverted by corona charging or the polarity of the color toner image formed on the photosensitive drum 10 is inverted by corona charging, Since the toner of the lower layer is not sufficiently charged to the same polarity, the transfer becomes unfavorable.

The reversal development is repeated on the photosensitive drum 10, and the color toner images of the same polarity formed by superimposition are collectively transferred to the toner image receiving member 14a without changing the polarity, and then recorded without changing the polarity. Batch transfer to paper P is preferable because it contributes to improving the transferability of backside image formation. Also for the surface image formation, reversal development is repeatedly performed on the photosensitive drum 10 to collectively transfer color toner images of the same polarity formed by superimposition onto the recording paper P without changing the polarity.
It is preferable because it contributes to improvement of the transferability of surface image formation.

From the above, in the color image formation, the first transfer means is operated to form a color toner image on the surface of the transfer material by using the above-described image forming method for the front surface and the back surface. A two-sided image forming method of forming a color toner image on the back surface of the transfer material by operating the second transfer means is preferably employed.

The toner image receiving member 14a has a thickness of 0.5-2.
An endless rubber belt of 0 mm, a semiconductive substrate of silicon rubber or urethane rubber having a resistance value of 10 ⁸ to 10 ¹⁴ Ω · cm, and a thickness of 5 to 50 μm as a toner filming prevention layer outside the rubber substrate. And a two-layer structure with fluorine coating. This layer also preferably has a similar semiconductivity. 0.1-0.5 thickness instead of rubber belt base
mm semi-conductive polyester, polystyrene, polyethylene, polyethylene terephthalate, polyimide, or the like can also be used.

The recording paper P on which the color toner images are formed on both sides is used as a paper separating AC neutralizer 14h for separating the transfer material.
(Hereinafter, also referred to as a separation pole), is separated from the toner image receiving body 14a, and is conveyed to a fixing device 17 as a fixing unit including two rollers having heaters inside both rollers. By applying heat and pressure between the fixing roller 17a and the pressure roller 17b, the toner adhered to the front and back of the recording paper P is fixed, and the recording paper P on which double-sided image recording has been performed is sent by the paper discharge roller 18. And discharged to a tray outside the apparatus.

The toner remaining on the peripheral surface of the toner image receiver 14a after the transfer contacts and contacts the toner image receiver 14a provided in a toner image receiver cleaning device 14i as cleaning means for the toner image receiver. It is cleaned by a blade that can be released. Further, the toner remaining on the peripheral surface of the photosensitive drum 10 after the transfer is subjected to static elimination by the image forming body AC static eliminator 16, and then enters the cleaning device 19 or is made of a rubber material that has contacted the photosensitive drum 10. Cleaning device 1 by cleaning blade 19a
Then, the sheet is scraped into the sheet 9 and waits for the next image formation.

Next, the circuit configuration of the image processing section B will be described with reference to the block diagram of FIG.

In the image reading section A, the image pickup device CCD
The analog image signals of three colors separated by color output from
After being converted into a digital image signal by the / D converter B11, in image processing (I) B12, in addition to γ correction processing according to the characteristics of the image forming apparatus, extraction of the effective image area of the document, frame erasure and fold erasure The image data is stored in the memory B14 after the image data is processed by performing image processing such as area processing.

Since a larger amount of image data is stored in the memory B14, the image data is compressed and stored in the image compression B13, and when read out from the memory B14, the image is expanded and output by the image expansion B15. Has become.

The image processing section B performs image processing according to a command from the control section B10. The control unit B10 determines whether the image data output from the memory B14 is a front image or a back image when forming an image, based on information from the front / back determination unit B20, and outputs the image output from the memory B14. Image processing corresponding to the front or back image data is performed.

The operation panel of the image forming apparatus has selection buttons for selecting one-sided originals to two-sided images, two-sided originals to two-sided images, and the like. The front / back determination means B20 determines the front / back image of the image data decompressed from the memory.

In the image processing (II) B16, color processing such as masking, inking, UCR, and γ conversion are performed, and then multi-value processing is performed.
Is output to At this time, since the back side image is subjected to two transfer steps with respect to the front side image which is subjected to one transfer step, there is a slight difference in image density and image quality. Therefore, there is a difference in γ correction between the front side and the back side. Processing is performed.

In the double-sided image forming apparatus of the present invention, there are front / back original image area information B21 and transfer material image area information B22, and these information are input to the control unit B10. The front / back original image area information B21 is detected by the image reading unit A by a detection unit provided on the feeding path of the document shape fed onto the platen glass 55, and the transfer material image area information B
Reference numeral 22 is input by using a recording paper selection button provided on the operation panel as a push button. The original may be placed directly on the platen glass 55, and the recording paper may be fed manually, so that such information is manually input. In the double-sided image forming apparatus of the present invention, the data selector (I) B17 performs the following rotation processing at the time of toner image formation of image data based on the front / back original image area information and the image area information of the transfer material. Do.

When forming the toner image on the transfer material, when the effective image area of the original image is in the same direction as the effective image area of the transfer material at the time of forming the back image, the original image is formed at the stage of forming the toner image on the back face. Mirror the image.

In forming a toner image on a transfer material, when the effective image area of the original image is perpendicular to the effective image area of the transfer material at the time of surface image formation, the original image is formed at the stage of forming the toner image on the surface. Rotate the image 90 degrees.

When forming the toner image on the transfer material, when the effective image area of the original image is perpendicular to the effective image area of the transfer material at the time of forming the back image, the original image is formed at the stage of forming the toner image on the back face. The image is rotated 90 degrees and the mirror image is rotated.

FIGS. 5A and 5B show the rotation processing at the time of forming the toner image of the original image of FIG. 5A. FIG. 5A shows the rotation processing at the time of forming the backside image, and FIG. Is shown. FIG. 6 schematically shows a data reading method when performing rotation processing (reading) on page data of an original image.

FIG. 6A is shown for comparison, and shows that the normal reading method (non-rotation) of the page data of the original image is performed by reading in the direction of the arrow. FIGS. 6B to 6D show a method of reading the page data of the original image when the rotation processing is performed, and FIG. 6B shows the method when the mirror image rotation is performed.
FIG. 6C shows a reading method when the image is rotated by 90 degrees, and FIG. 6D shows a reading method when the image is rotated by (mirror image + 90 degrees). In the data selector (I) B17, the above rotation processing is performed on the front side image data and the back side image data in accordance with an instruction from the control unit B10.

Following the data selector (I) B17, a front side output memory B18A and a back side output memory B18B are provided. When an image output instruction is issued from the control unit B10, the front side memory B14 is called. Is processed by image processing (II) B16, and is rotated by 90 degrees depending on conditions by the data selector (I) B17.
A, then the image data of the back side is subjected to mirror image rotation processing or (mirror image + 90 degrees) rotation processing according to conditions, and then input to the back side output memory B18B.

Then, in accordance with the timing of double-sided image formation in the image forming apparatus, first, the backside image data is output from the backside output memory B18B to the exposure unit 12 by the data selector (II) B19, An image is formed. Then the data selector (I
I) The surface image data from the surface output memory B18A is output to the exposure unit 12 by B19, and the surface image is formed.

FIG. 7 shows image processing when the effective image area of the transfer material with respect to the effective image area of the original image has the same directional relationship. The normal data reading (non-rotation) is performed at the stage where the toner image is formed, so that an appropriate double-sided image can be obtained on the transfer material.

FIG. 8 shows image processing when the effective image area of the transfer material is in a vertical direction with respect to the effective image area of the original image. This indicates that an appropriate double-sided image can be obtained on the transfer material by rotating the original image by 90 degrees at the stage of forming the toner image on the surface by rotating the original image at the same time as rotating the mirror image.

In the above description, the rotation processing of the page data of the original image is performed by the data selector (I) B17. However, the present invention is not limited to this. It is also possible to adopt a configuration in which this is performed following the extension B15.

In the above description, the image forming apparatus for forming a color image on both sides of the transfer material has been described. However, a monochrome image may be used. In this case, no color correction is required, and the image processing is simplified.

In the present invention, attention is paid to the direction of the effective image area of the transfer material with respect to the effective image area of the original image, and the page data is rotated in the image processing corresponding to this. In addition, the size of the effective image area of the original image and the size of the effective image area of the transfer material are detected, and the two sizes are compared. Based on the comparison result, the magnification (magnification or magnification) of the original image at the time of image formation is determined. The effect of the present invention can be further enhanced by determining (reduction) and recording the image data of the original image on the transfer material without excess or deficiency.

[0067]

According to the present invention, regardless of the direction of the effective image area of the original image for forming an image on the front or back surface of the transfer material and the direction of the effective image area of the transfer material, it is always regarded as normal. A double-sided image forming apparatus in which an image is formed in a correct arrangement relationship is provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of an image forming apparatus of the present invention.

FIG. 2 is a side sectional view of an image forming body.

FIG. 3 is an explanatory diagram showing a state of forming a toner image.

FIG. 4 is a block diagram showing a circuit configuration of the present invention.

FIG. 5 is an explanatory diagram showing a rotation process when forming a toner image of an original image.

FIG. 6 is an explanatory diagram showing a data reading method when performing a rotation process.

FIG. 7 is an explanatory diagram illustrating image processing when an original image and a transfer material have the same directional relationship.

FIG. 8 is an explanatory diagram illustrating image processing when an original image and a transfer material are in a vertical direction relationship.

DESCRIPTION OF SYMBOLS 10 Photoreceptor drum 11 Scorotron charger 12 Exposure unit (image exposure means) 13 Developing device 14a Toner image receiver (intermediate transfer member) 14c Transfer device 14g Backside transfer device 14h Separation pole 15 Paper feed cassette A Image Reading unit B Image processing unit C Image forming unit B10 Control unit B12 Image processing (I) B14 Memory B16 Image processing (II) B17 Data selector (I) B18A Front side output memory B18B Back side output memory B19 Data selector (II) B20 Front / back determination means B21 Front / back original image area information B22 Transfer material image area information

Claims (6)

[Claims] An image forming unit that forms a toner image on a surface of the original image by a toner image forming unit; and a first image carrying unit that carries the toner image; and a toner image that is carried on the first image carrying unit. Are collectively transferred, and a second image carrying means for carrying the transferred toner image on the surface, and a toner image carried by the first image carrying means on one surface (front surface) of a transfer material A first transfer unit that transfers the toner image carried by the second image carrying unit to the other surface (back surface) of the transfer material; and both surfaces of the transfer material. A two-sided image forming apparatus having a fixing device for fixing a toner image transferred onto a transfer material, wherein an effective image area of an original image with respect to an effective image area of the transfer material at the time of forming a back image when forming a toner image on the transfer material Are in the same direction, the toner image on the back Double-sided image forming apparatus characterized in that to the original image mirror rotating at the stage of formation. 2. A first image carrying means for forming an original image on a surface thereof as a toner image by a toner image forming means and carrying the toner image, and a toner image carried on the first image carrying means. Are collectively transferred, and a second image carrying means for carrying the transferred toner image on the surface, and a toner image carried by the first image carrying means on one surface (front surface) of a transfer material A first transfer unit that transfers the toner image carried by the second image carrying unit to the other surface (back surface) of the transfer material; and both surfaces of the transfer material. A fixing device for fixing a toner image transferred to a transfer material, wherein an effective image area of an original image with respect to an effective image area of the transfer material at the time of surface image formation when forming a toner image on the transfer material Are in the vertical direction, the toner image on the surface Double-sided image forming apparatus wherein rotating the original image 90 degrees at the stage of formation. 3. A first image carrying means for forming an original image on a surface thereof by a toner image forming means as a toner image, and carrying the toner image, and a toner image carried on the first image carrying means. Are collectively transferred, and a second image carrying means for carrying the transferred toner image on the surface, and a toner image carried by the first image carrying means on one surface (front surface) of a transfer material A first transfer unit that transfers the toner image carried by the second image carrying unit to the other surface (back surface) of the transfer material; and both surfaces of the transfer material. A two-sided image forming apparatus having a fixing device for fixing a toner image transferred onto a transfer material, wherein an effective image area of an original image with respect to an effective image area of the transfer material at the time of forming a back image when forming a toner image on the transfer material Is in the vertical direction, the toner image on the back Double-sided image forming apparatus, wherein the rotating mirror image rotates the original image by 90 degrees at the stage of formation. 4. A first image carrying means for forming an original image on a surface thereof by a toner image forming means as a toner image, and carrying the toner image; and a toner image carried on the first image carrying means. Are collectively transferred, and a second image carrying means for carrying the transferred toner image on the surface, and a toner image carried by the first image carrying means on one surface (front surface) of a transfer material A first transfer unit that transfers the toner image carried by the second image carrying unit to the other surface (back surface) of the transfer material; and both surfaces of the transfer material. A two-sided image forming apparatus having a fixing device for fixing the toner image transferred to the toner image, forming a toner image on the back surface when the effective image area of the transfer material is in the same direction as the effective image area of the original image. The feature is to rotate the original image at the stage of mirroring Double-sided image forming apparatus. 5. A first image carrying means for forming an original image on a surface thereof by a toner image forming means as a toner image, and carrying the toner image; and a toner image carried on the first image carrying means. Are collectively transferred, and a second image carrying means for carrying the transferred toner image on the surface, and a toner image carried by the first image carrying means on one surface (front surface) of a transfer material A first transfer unit that transfers the toner image carried by the second image carrying unit to the other surface (back surface) of the transfer material; and both surfaces of the transfer material. A two-sided image forming apparatus having a fixing device for fixing the toner image transferred to the toner image, forming a toner image on the back surface when the effective image area of the transfer material is perpendicular to the effective image area of the original image. And rotate the original image 90 degrees By image rotation, the double-sided image forming apparatus characterized by rotating the original image 90 degrees forming a toner image on the surface. 6. An image processing method for rotating a toner image formed on the surface of the first image bearing means, wherein the original image is temporarily stored in a memory, and thereafter, is performed behind the memory. 6. The double-sided image forming apparatus according to any one of 5.